Expansible rotary drill bit

ABSTRACT

An expansible rotary drill bit and method of using the same, wherein the expansible cutters are hydraulically held open by a quantity of liquid in a chamber between the mandrel of the bit and the cutter supporting body, the fluid being trapped in the chamber by a sleeve which closes ports in the mandrel, the sleeve being shiftable to open the ports to allow retraction of the cutters. Tools are provided for moving the sleeve in and pulling the sleeve from the mandrel of such a bit. A method is employed that uses such a bit in an air drilling operation, including the steps of filling the chamber with a fluid after lowering the bit in a drilled hole, and pressurizing the chamber to expand the cutters, and then trapping the fluid in the chamber.

United States Patent Inventor Archer W.K ammerer, Jr. 3 ,208,5 32 9/ l965 Chenoweth 166/1 96X Fullerton,.Calif. 3,339,647 9/1967 Kammerer175/268 1968 Primary Examinerlan A. Calvert l g B Patented Mar. 1971Attorney ernard Krlegel Assignee Baker Oil Tools, Inc.

City of Commerce, Calif.

ABSTRACT: An expansible rotary drill bit and method of EXPANSIBLE ROTARYDRILL BIT using the same, wherein the expansible cutters are hydrauli-18 Cl 6 Bra in Fi s. Cally held open by a quantity of liquid in achamber between aims, w 3 g the mandrel of the bit and the cuttersupporting body, the fluid US. Cl. 175/268, being trapped in the chamberby a sleeve which closes ports in 175/290 the mandrel, the sleeve beingshiftable to open the ports to Int. Cl. EZlb 9/32 allow retraction ofthe cuttem Tools are provided for moving F leld of Search 175/267- thesleeve in and pulling the sleeve f the mandrel f such a 269, 290; 196bit. A method is employed that uses such a bit in an air drilling 7operation, including the steps of filling the chamber with a ReferencesCited fluid after lowering the bit in a drilled hole, and pressurizingUNITED STATES PATENTS the chamber to expand the cutters, and thentrapping the fluid 2,755,070 7/1956 Kammerer 175/267 in the chamber.

x .4 l7 3 I6 4327 30 ,1 I; I, I g a I we l EXPANSHBLE ROTARY DRILL BITin the drilling of certain boreholes into the earth, rotary expansibledrill bits have been employed which are adapted to be connected to arotary drill string, through which drill string drilling fluid iscirculated to flush cuttings from the borehole as the drillingprogresses, the drill bits being so constructed that a differentialpressure is caused by the flow of the drilling fluid through arestriction in the drill bit, this differential pressure serving toeffect outward expansion of the cutters of the drill bit. 7

In the drilling of some earth formations which are incompetent and tendto cave in or slough off into the borehole, a casing or other liner ortubular pile may be lowered during the drilling operation as theborehole'progresses. An example of such borehole drilling operations isthe provision of piles in boreholes in earth formation which is notreadily susceptible to the driving of piles.

However, when a gaseous fluid is employed as the drilling fluid, thecreation of sufficient differential pressure to effect the expansion ofthe bit cutters poses a problem. In addition, even following initialexpansion of the bit cutters, it sometimes becomes necessary to retrievethe bit from the borehole by allowing the cutters to move to retractedpositions so that the bit may be moved upwardly through'the pile orcasing in the previously drilled borehole. On the other hand, thecutters of such bits may be allowed to move to the retracted positionwhen additional lengths of drill string or drill pipe are being added.

The present invention provides a rotary expansible drill bit of the typehaving expansible cutter elements movable outwardly from retractedpositions, wherein hydraulic means are provided for releasably holdingthe cutters in expanded positions.

More particularly, the invention. provides such a drill bit in which acutter-supporting body and a mandrel define therebetween a chambercommunicating with a'p'assage in the mandrel through lateral ports whichare closable by, asleeve shiftable within the mandrel passage between afirst position at which the ports are closed and a second position atwhich the ports are open, so as to trap a liquid in the chamber when thebody and mandrel are in positions causing expansion of the cutters, andfor allowing the fluid to bleed from the'chamber so as to enablemovement of the bit body and mandrel to relative positions permittingretraction of the cutters.

Thus, a rotary expansible bit in accordance with the invention may beemployed to drill a borehole through incompetent earth formation, whilea casing or other liner or pile is lowered into the borehole as thelatter progresses, so as to confine the sidewalls of the boreholeagainst cave-in or sloughing off. However, when it is desired to removethe bit from the borehole, either following drilling of the borehole toits total depth or when it is necessary to service the bit, the sleevemay be shifted to a position allowing the cutters to be retracted sothat the bit is free to pass upwardly through the casing or pile.

The invention also provides a shifting tool adapted to be run into thebit through the drill string into engagement with the sleeve when it isin its port-closing position, in order to move the sleeve to its secondposition at which the ports are open.

More particularly, the invention provides such a shifting tool which isalso capable of moving the sleeve from the position at which the portsare open to the position at which the ports are closed, so as to trapliquid in the bit chamber to maintain the cutters expanded.

The invention also provides a pulling tool enabling removal of thesleeve entirely from the mandrel passage, following removal of the bitfrom the borehole, to allow service of the bit.

in addition to the foregoing, the invention provides a method ofdrilling boreholes into the earth employing an expansible rotary drillbit, wherein a casing or pile is lowered into the borehole above the bitand in which the bit is maintained in an expanded condition by trappedliquid in a chamber in the bit. in this connection, the inventioncontemplates plugging off the drilling fluid passage through the bitmandrel and filling or partially filling the drill string with a liquid,and, thereafter, applying air or other gas of fluid pres sure to theliquid in the drill string to effect expansion of the bit cutters, and,with the cutters expanded, running into the bit passage a tool capableof moving a sleeve to a position within the passage preventing theescape of liquid from the bit chamber, the plug then being removed fromthe bit passage to allow the resumption of circulation of drilling fluidtherethrough.

This invention possesses many other advantages and has other purposeswhich may be made more clearly apparent from a consideration of a formand method embodying the invention. This form and method are shown anddescribed in the present specification and in thedrawings accompanyingand constituting a part thereof. They will now be described in detail,for the purpose of illustrating the general principles of the invention;but it is to be understood that such detailed description is not to betaken in a limiting sense, since the scope of the invention is bestdefined by the appended claims.

Referring to the drawings:

FIG. 1 is a longitudinal section illustrating a rotary expansible drillbit in accordance with the invention, with the cutters expanded to drilla borehole in which a casing or pile is being lowered as the drillingprogresses;

FIG. 2 is a view corresponding to FIG. I, but showing the cutters in aretracted condition;

FIG. 3 is a fragmentary, longitudinal section showing the bit mandreland body in the position at which the cutters are expanded, but with ashifting tool disposed in the bit passage and the sleeve moved to aposition allowing communication between the bit chamber and the passage;

FIG. 4 is a view generally corresponding to FIG. 3, but showing theshifting tool in a position engaged with the sleeve to move the same toa position closing the ports;

FIG. 5 is a fragmentary, longitudinal section illustrating the mandreland body in a position at which the cutters are retracted, and showing asleeve-pulling tool engaged in the sleeve preparatory to pulling thesleeve from the bit passage;

and

FIG. 6 is a view corresponding to FIG. 5, showing the sleeve pullingtool in condition for pulling the sleeve from the bit passage. I

As shown in the drawings, a rotary expansible drill bit A is secured tothe lower end of a string of drill pipe B extending to the top of aborehole C, and by means of which the drill bit is lowered or elevatedthrough a string of casing, or other liner or pile D.

The upper portion of the rotary drill bit consists of a mandrel 10having an upper pin 11 threadedly connected to the lower end of thestring of drill pipe B. This mandrel includes an upper kelly member 12slidably engaged in the main body 13 of the drill bit. The exterior ofthe lower portion 14 of the kelly is noncircular in shape, beingtelescopically received in a companion noncircular socket 15 formed inthe main bit body l3. Specifically, the kelly exterior and the socket 15may be of hexagonal shape to enable the kelly 12 to be movedlongitudinally with respect to the body 13, while still being capable oftransmitting rotary motion'to the body.

The mandrel 10 has a limited range of longitudinal movement within thebody, its downward movement being determined by engagement of the lowerend 16 of the kelly with an inwardly directed body shoulder 17, and itsrelative upward movement being limited by engagement of an externalshoulder or piston portion 18 of the kelly with a cylinder head 19secured to the body. The upper end of the head has a flange 20 engaginga body shoulder 21, the head 19 being prevented from moving upwardly ofthe body by split snap retainer rings 22 fitting in a body groove 23 andoverlying the flange 20. An annular guide 24 is releasably secured tothe body 13 by a split snap ring 25 above the retainer rings.

The body 13 has a plurality of expansible parts mounted on it. Theseinclude cutler supporting members 25 pivotally mounted in one or morebody slots 27 on hinge pins 28 which are suitably secured to the body toprevent their loss therefrom. Each cutter supporting member 26 dependsfrom the hinge pin 28 and carries a rotary cutter 29 on its lower end.

The cutter supporting members 26 and the cutter structures 29 themselvestend to occupy a retracted position substantially entirely within theconfines of the main body 13 of the bit. These cutter supporting membersand the cutter structures are expansible outwardly to engage and drillaway a borehole shoulder E, as seen in FIG. 1. To accomplish theexpansion, each cutter supporting member 26 has an inclined expandersurface 30 on its inner portion below the hinge pin 28, which tapers ina downward and inward direction. Each expander surface terminates in alock surface 31 formed on a lock portion 32 of the cutter supportingmember. The outward expansion is accomplished by producing relativelongitudinal movement between the mandrel and the body 13, which willproduce relative longitudinal movement between the cutter supportingmembers 26 and a tubular portion 33 of the mandrel 10. The tubularportion 33 includes a lower portion 34 slidable within an elongate guidebushing 35 mounted in a bridge 36 secured in the body and extendingacross the body slot or slots 27. The guide bushing 35 is disposed belowthe lock portions 32 of the cutter supporting members 26 and is securedin place by upper and lower contractable split retainer rings 35a, 35bdisposed in grooves in the bushing and engaging the upper and lower endsof the bridge 36.

Located initially substantially above the guide bushing 35 and below thehinge pins 28 and in cutter supporting member recesses 37 is a mandrellock and expander 38, which has outer surfaces 39 adapted to engage theexpander surfaces 30 and the lock surfaces 31. The lock and expander 38may be formed integral with the tubular member 33, the upper end of thelatter being piloted within a socket 40 formed in the lower portion 14of the kelly 12. An enlarged boss 41 on the tubular member 33 engages adownwardly facing shoulder 42 of the kelly, the tubular member beingheld against this shoulder by a suitable split retainer or lock ring 43snapped into an internal groove 44 encompassing the kelly socket andengaging the lower end of the tubular member boss 41.

A gaseous drilling fluid, drilling mud, or other suitable fluid can passdown through the central passage 45 in the kelly 12 from the drillstring 8 and into the central passage 46 extending completely throughthe tubular member 33. Leakage of fluid around the exterior of thetubular member 33 is prevented by a suitable side seal ring 47, such asa rubber or rubberlike O-ring in a peripheral groove 48 in the kelly,which engages the exterior of the boss 41.

Assuming the body of the tool to be elevated relatively along thetubular mandrel 10, as seen in FIG. 1, the inclined expander surfaces 30of the cutter supporting members 26 will shift upwardly along the lockand expander portion 38 of the tubular member 33. During such upwardshifting, the cutter supporting members 26 and the cutter structures 29carried thereby will pivot about the hinge pins 28 and be urged in anoutward direction. The upward movement of the body 13 with respect tothe mandrel 10 can continue until the cutter structures 29 have beenshifted outwardly to their fullest extent, as determined by engagementof stop shoulders 49 on the cutter supporting members 26, with companionshoulders 50 formed in the body on opposite sides of the body slot orslots 27. When such engagement occurs, the lower end 16 of the kellyportion 12 of the tubular mandrel will engage the body shoulder 17 andthe lock and expander 38 on the tubular member 33 will be disposedbehind and in engagement with the lock portions 32 of the cuttersupporting members 26.

It is to be noted that the surfaces 31 of the lock portions 32 of thecutter supporting members 26 and the companion surfaces 39 on the lockand expander portion 38 of the tubular member are substantially parallelto the axis of the drill bit, when the cutters 29 are fully expanded, toprevent reactive forces on the cutter structures 29 from moving thelatter inwardly. As a practical matter, it is preferred that thecoengaging lock surfaces 39, 31 be inclined slightly in a downwarddirection toward the axis of the tool to insure release of the lock andthe expander portion 38 from the cutter supporting members 26, when thelatter and the cutter structures 29 are to be shifted to retractedposition.

The piston or enlarged portion 18 on the drill stem 12 is receivedwithin a counterbore 51 formed in the upper portion of the body of thetool. This upper portion actually constitutes a cylinder 52 having acylindrical wall 53 extending from a lower shoulder 54 defining thebottom of the counterbore to the cylinder head 19. A confined cylinderspace or chamber 55 is formed between the piston portion 18 of thekelly, the periphery of the kelly above the piston, and the cylinder 52.A suitable packing or side seal ring 56 may be provided on the piston18, which is adapted to slidably seal against the cylindrical wall 53 ofthe cylinder 52. Fluid is thereby prevented from passing in a downwarddirection between the piston and the cylinder. Similarly, fluid isprevented from passing in an upward direction out of the annularcylinder space 55 by an inner side seal ring'58 on the cylinder head 19slidably and sealingly engaging the periphery of the kelly above thepiston 18, and also by an outer side seal ring 60 disposed in the head19 and sealingly engaging the cylinder wall 53.

Fluid under pressure in the string of drill pipe B and in the tubularmandrel passage 45 can be fed into or bled from the cylinder space 55through one or more side ports 62 establishing communication between thecentral passage 45 through the kelly and by cylinder space. Such fluidunder pressure may be developed, in the illustrative bit, by restrictingthe flow of fluid through the kelly 12 and its companion tubular member33 by means of a flow control member 70 mounted in the lower portion ofthe mandrel. As a result of such restriction of flow, the pumping ofcompressed gas or drilling mud at an adequate rate through the apparatuswill build up a back pressure of fluid in the passage 45, which pressurewill be imposed on the fluid in the cylinder space 55, acting upon thecylinder head 19 to urge the body 13 of the tool in an upward directionwith respect to the tubular mandrel 10 to secure outward expansion ofthe cutter supporting members 26 and cutter structures 29 to theirfullest extent, as above described.

As apparently disclosed in the drawings, a pair of diametrically opposedsupporting members 26 and cutter structures 29 is supplied, such devicesbeing disposed substantially from each other. Actually, it is preferredto have a drill bit with three sets of supporting members and cutterstructures spaced substantially l20 from each other, to secure asmoothly running device. The two sets of supporting member structuresand slots 27 in which they are disposed are shown in the interest ofsimplicity of the drawings.

In the event that the use of the flow restrictor is to be relied on insome types of drilling operations to effect cutter expansion, the flowof fluid through the drill bit is greatly restricted. After full cutterexpansion has occurred, a greater quantity of fluid is permitted to flowthrough the bit. As shown, the flow control member 70, which may be madeof a suitable hard material, such as tungsten carbide, is pilotedupwardly within a downwardly facing counterbore 76 in the lower end 34of the tubular member 33 of the mandrel. Below the end of the tubularmember 33, the flow control device 70 is enlarged in diameter to providea head 77 conforming to the internal diameter of the guide bushing 35and capable of sliding therealong. The flow control member 70 is securedto the tubular member 33, as by use of welding material 7 8.

The flow control member has a central passage 79 of a comparativelylarge diameter opening upwardly into the passage 46 through the tubularmember of the mandrel. This central passage terminates in a lower endwall of the control member having a choke orifice 81 extendingtherethrough communicating with the central passage 79 and openingdownwardly through the end wall into the body slots 27. Above thecentral orifice 31, the head of the flow control member has side portsor nozzles 82 communicating with the central passage 79 and openingthrough the periphery of the head 77, these side ports having areassubstantially greater than the area through the central orifice 81. Theside ports 82 are circumferentially spaced from one another to the sameextent as the cutter supporting members 26 and are aligned with theslots 27, so that when the ports 92 of the flow control member aredisposed below the guide bushing 35, the ports or nozzles can dischargefluid through the slots 27 toward the expanded cutter members 29 to cooland clean them and flush the cuttings upwardly around the drill bit Aand the drill pipe B to the top of the borehole.

When the cutters 29 are in their retracted position, such as disclosedin E16. 2, the mandrel and its tubular member 33 are in an upperposition with respect to the body 13 of the tool and the guide bushing35 secured thereto, to close the side ports or nozzles 82 of the controlmember. As a result, all of the fluid pumped down through the drillstring B and the mandrel passage 45, 46 must pass out through the chokeorifice 81 of relatively small diameter, causing a comparatively largeback pressure to be built up in the fluid within the kelly 12, whichpressure is transmitted to the fluid in the ports 62 and the cylinderspace 55 for upward action on the cylinder head 19, to elevate the body13 and cutters 26, 29 with respect to the mandrel 10, the cutterstructures 26, 29 moving upwardly along the expander member 38 andshifting outwardly, as described hereinabove, at which time the ports 82are exposed (FIG. 1).

The bit A, as thustfar described, is adapted for use with the cutters 29positively held in the expanded condition of FIG. 1, and as the boreholedrilling progresses, the casing or pile D may be lowered into theborehole, its lower end being immediately above the bit. Thus, the ports62 leading between the cylinder space or chamber 55'and the centralpassage 45 in the mandrel 10 are closable by a valve sleeve 90, which isslidably disposed in the passage 45. The sleeve90 has suitable upperside seal rings 91 and lower side seal rings 92 sealingly engaged withthe wall of the passage 45. Between the seal rings 91 and 92, the sleeve90 has an imperforate central portion 93 which effectively closes themandrel ports 62 when the sleeve is in the upper position of FIG. 1, butthe sleeve being movable to a lower position, as seen in FIG. 2 when itis desired that the cutters be capable of retraction. When the. sleeve90 is in its upper position, it may confine or trap'in the cylinderspace or chamber 55 a quantity of liquid, such as oil or water, or otherliquid, the mandrel 10 and body 13 of the vbit thereby beinghydraulically locked in relative longitudinal positions at which thecutters 29 are expanded. However, when the sleeve 90 is moved downwardlyto the lower position of FIG. 2, the ports 62 can communicate with thepassage 45 in the mandrel to allow bleeding off of fluid from thechamber 55 and movement of the mandrel l0 and body 13 relativelylongitudinally to the position shown in FIG. 2, at which the cutters 29are retracted.

Latch means 95 are provided on the sleeve 90 cooperable with the mandrel10 for releasably holding the sleeve 90 in its upper position to preventinadvertent movement of the sleeve 91). This latch means 95 isillustrated as including an annular groove 96 in the inner wall of themandrel 10 and having an upper, upwardly inclined surface 97 and alower, downwardly inclined surface 98. The sleeve 99 has a number offlexible latch arms 99 integral therewith and projecting upwardlytherefrom,.these arms being interconnected at their upper ends by anannular head 100 which is also integral with the arms 99. These arms 99are provided, in the illustrative assembly, by longitudinally slottingthe upper portion of the sleeve 90 at a suitable number of angularlyspaced locations, as at 1191, and by reducing the thickness of the armsto render them relatively flexible. Each arm 99 has an outer latchelement or lug 102 having an upper inclined face 103 and a lowerinclined face 104, whereby the lugs 102 are complementally engageable inthe channel 96 in the mandrel passage 45. However, the upper surface 97of the groove 96 and the upper surface 103 of the lugs 102 can cam thefingers inwardly responsiv'e to upward movement of the sleeve from thelatched position; and the lower channel surface 98 and the lower lugfaces 104 can cam the fingers inwardly responsive to downward movementof the sleeve 90 from the latched position.

Referring to FIGS. 3 and 4, a tool T is illustrated for shifting thesleeve 90 downwardly from the latched position to allow opening of thechamber 55 when the cutters 29 are to be retracted, and for moving thesleeve upwardly back to the latched position when fluid is to be trappedin the chamber 55.

This tool T comprises a tool mandrel in the form of an elongated rodhaving a threaded upper end 111 connectable to a sinker bar 112 or otheradapter, whereby the tool T may be lowered through the pipe string Binto the passage 45 in the bit mandrel 10 on a string of rods or wireline (not shown). At its lower end, the tool mandrel 110 has a shoulder113, and between the threaded end 111 and the shoulder 113, the toolmandrel 110 is provided with a reduced diameter section 114. Thisreduced diameter section 114 lies between an upper cylindrical section115 and a lower cylindrical section 116 of the tool mandrel 110.Slidably disposed on the cylindrical mandrel sections 115 and 116 andspanning the reduced diameter section 114 is an elongated member,generally denoted at 117, which provides means for engaging the valvesleeve 90 to shift the same between its upper and lower positionsresponsive to opposite longitudinal movement of the tool mandrel 110.More particularly, the member 117 comprises an elongated tubular body118 having an outwardly enlarged flange or head 119 at its upper end. Ata plurality of circumferentially spaced locations, the member 117 islongitudinally slotted, as at 120, to provide a number ofcircumferentially spaced, longitudinally extended resilient arms 121.Each of the arms 121 between its ends has an outwardly projecting lug122, and at their lower ends the arms 121 are interconnected by a lowercontinuous portion 123 of the member 117. The lugs 122 on the arms 121of the tool T project outwardly for cooperative engagement with internallug portions 102a of the lugs 102 of the flexible arms 99.

As seen in FIG. 3, when the tool T is lowered into the passage 45through the bit mandrel 10, the lower end of the tool mandrel 110 willpass through the valve sleeve latch means 95, as will the arms 121 ofthe tool member 117. When the valve sleeve 90 is in the upper position,with the lugs 102 of the latch arms 99 engaged in the annular groove 96in the bit mandrel 10, the lugs 122 on the tool fingers 121 may freelypass through the inner lugs 102a of the latch fingers 99, the enlargedhead 119 of the tool member-117 coming into abutment with the upper endportion 100 of the latch means 95, to impose a downward force on thevalve sleeve 90 and move the latter downwardly to the position shown inFIG. 3. Such downward movement of the valve sleeve 90 opens the bitmandrel passages or ports 62 to allow communication between the chamber55 and the bit mandrel passage 45. Under these circumstances, the bitbody 13 is free to move downwardly relative to the bit mandrel 10, theliquid flowing from the chamber through the ports, allowing the cuttersupporting members 26, as previously described, to swing inwardly andmove the cutters 29 to their retracted position. The cutters will remainin the retracted position to allow the drill string B to be pulledupwardly through the casing C, if the drilling is completed, or to allowservicing of the bit.

Following removal of the bit upwardly through the casing or pile D withthe bit cutters retracted, it may be desired to run the same or anotherbit back into the borehole through the casing or pile D, with thecutters in the retracted position. However, when the bit is disposed atthe desired location in the borehole where drilling is to be resumed, itis necessary to effect reexpansion of the bit. In the event that thenature of the drilling fluid circulation system being employed or thevolume of available air, in the event that air or other gas is employedas the drilling fluid, is suflicient to allow the differential pressureactuation of the bit, as previously described, the bit cutters willinherently be expanded when the circulation of drilling fluid resumes.

However, the present invention contemplates trapping within the chamber55 of the bit assembly a quantity of liquid to maintain the bit cuttersin the expanded condition even when there is insufficient drilling fluidpressure to do so, and even if the circulation of fluid ceasescompletely, in which event there could be no pressure in the mandrelpassage 45.

Thus, as also seen in FIG. 3, a plugging device 125 may be placed in thebit passage 45 or dropped into the drill string to seat in the passage45 when it is desired to effect expansion of the bit cutters. Underthese circumstances, it will be understood that the tool T, also shownin FIG. 3, would not be present since the tool T would have been removedfrom the bit assembly while at the top of the borehole. This pluggingdevice 125 includes a cylindrical lower body section 126 having suitableside seal rings 127 engaging the wall of the passage 46 in the tubularmandrel section 33. The plugging device 125 also includes an enlargedtapered portion 128 adapted to land in the throat 100a leading into thepassage 46 through the boss 41 of the mandrel section 33. At its upperend, the plugging device 125 has a neck 129 provided with a head 130adapted to be engaged by a suitable recovery tool (not shown), which canmove downwardly through the drill string B and into the bit mandrelpassage 45 to engage the recovery head 130 and effect upward removal ofthe plugging device 125.

With the plugging device in place preventing downward flow of fluidthrough the bit assembly, the cutters 29 may be expanded by filling thedrill string B to the necessary extent with a liquid, such as water oroil, and the body of liquid in the drill string may be sufficientlypressurized as to effect expansion of the bit cutters by the applicationof pressure in the chamber 55 upwardly against the cylinder head 19 anddownwardly against the annular piston 18 which is relatively shiftablein the cylinder 52 defining the chamber 55. After the cutters have beenexpanded responsive to relative longitudinal movement of the bit mandrel10 and the bit body 13 to the positions shown in FIG. 1, the tool T,previously described as being adapted to move the valve sleeve 90 to thelower position of FIG. 3, is run into the bit passage 45 through thedrill string B, the lugs 122 causing the tool arms 121 to flex inwardlyinto the reduced diameter region 114 of the tool mandrel 110, as thelugs 122 engage and pass below the internal lugs 102a of the latchfingers 99 of the valve sleeve 90.

Thereafter, the tool T will be moved upwardly as shown in FIG. 4, thelower cylindrical section 116 of the tool mandrel 110 moving upwardly inthe arms 121 ofthe tool member 117 and behind the lugs 122 to preventtheir inward deflection (FIG. 4), the shoulder 113 at the lowerextremity of the tool mandrel having engaged the lower end 123 of thetool member 117. Under these circumstances, the reduced diameter section114 of the tool mandrel 110 will have been moved upwardly so that thetool arms 121 are no longer inwardly flexible. Therefore, the externallugs 122 on the arms 121 will engage beneath the internal lugs 102a ofthe latch fingers 99 to effect upward movement of the valve sleeve 90until the external lugs 102 on the latch fingers 99 arrive at theinternal groove 96 within the bit mandrel 10, snapping into the groove.At this time, the sleeve 90 is in its port closing position, and isreleasably held against further movement in either direction bycoengagement of the latch lugs 102 with the sides 97, 98 of the groove96. Thereupon, however, the tool T may pass upwardly from the latchmeans 95, since the outward movement of the inner lugs 1020 of the latchfingers 99, when the latch means is engaged in the internal groove 96,will allow upward movement of the external lugs 122 of the tool T pastthe lugs 102a, releasing the tool T from the latch means. Thus, sincethe sleeve 90 is across the ports 62 the cutters 29 will behydraulically locked in expanded positions. Thereafter, a wire line orother recovery tool will be run in through the drill string into the bitto engage the recovery head 130 of the plugging device 125, pulling itfrom the bit assembly to the top ofthe hole, allowing further drillingoperations to resume.

When the bit assembly is at the top ofthe borehole, and it is desired toremove the valve sleeve 90 from the bit passage 45 during servicing ofthe bit, as, for example, for the purpose of replacement of the sideseal rings 91 and 93 on the valve sleeve itself, the bit mandrel 10 andthe body 13 are shifted to the relative longitudinal positions shown inFIGS. 2 and 5, with the valve sleeve in the lower or port openingposition. A sleeve pulling tool P includes a tool mandrel 200 having athreaded upper end 201 for threaded connection with a connecting rod202, or other suitable device, for effecting longitudinal movement ofthe pulling tool. Intermediate its ends, the pulling tool mandrel 200has a reduced diameter section 203. Adjacent its lower end, the mandrel200 has an enlarged cylindrical section 204 and a further enlarged lowercylindrical section 205. Slidably disposed about the tool mandrel 200between the further enlarged cylindrical section 205 and a shoulder 206at the lower end of the rod 202 is a colletlike device 207 having anupper annular ring 208 provided with a plurality of downwardly extendedand circumferentially spaced resilient arms 209, the lower ends of whichare provided with outstanding lugs 210. When the tool P is disposedwithin the passage 45 of the bit mandrel 10, the upper ring 208 of thepulling device 207 engages the upper head portion 100 of the latch means95 of the valve sleeve 90, the arms 209 ex tending downwardly to aposition at which the external lugs 210 are closely adjacent to theinternal lugs 102a of the latch arms 99. The normal outward projectionof the lugs 210 is such that they will expand beyond the diameter of thebore through the head 100 of the latch means 99, the head 100 providinga lower shoulder 1000 projecting inwardly and adapted to be engaged bythe pulling tool lugs 210 when the pulling tool P is moved upwardly, asseen in FIG. 6. The tool P is insertable through the head 100, since thelugs will flex inwardly and then expand outwardly to the position shownin FIG. 5.'The rod 202 and mandrel 200 are elevated to shift thecylindrical portions behind the lugs 210 and engage the mandrel shoulder204a with the lower ends of the lugs 210, preventing inward shifting ofthe lugs, thereby coupling the tool P to the sleeve 90. Upward movementof the tool P will withdraw the sleeve 90 from the mandrel 10.

While the pulling tool P has just been described as being useful for thepurpose of pulling the valve sleeve 90 from the bit assembly, while thebit assembly is at the top of the borehole, it will be understood thatthe sleeve may be pulled while the bit assembly is at the bottom of theborehole if it appears that such pulling of the sleeve is necessary ordesirable. In this connection, it will be understood that the rod 202 ofthe pulling tool P may be run into the drill string on a pipe or cableand the tool engaged with the latch means 95 of the sleeve 90, as shownin FIG. 5.

In the use of the present invention, the bit assembly A is connected toa lower bit F threadedly connected to the body 13 and capable of passingthrough the casing D to drill the hole within the shoulder E, the upperend of the bit A then being connected to the lower end of a length oftubular drilling conduit or drill pipe B with the cutters 29hydraulically locked in an expanded condition by trapped fluid in thechamber 55. As the drilling progresses, the casing or pile D is moveddownwardly in the borehole C behind the bit. If it becomes desirable toremove the bit assembly A from the borehole, it will be necessary toallow retraction of the cutters 29 to the position shown in FIG. 2.Under these circumstances, the tool T of FIGS. 3 and 4, or any otherappropriate tool capable of engaging the upper head 100 of the valvesleeve latch means 99, will be lowered through the drill pipe to engagethe head 100 to force the valve sleeve downwardly from its normallylatched condition, releasing the trapped fluid from the chamber 55. Thedrill string B is then moved upwardly, the body 13 of the bit assemblyremaining stationary, the expander and lock 38 on the lower mandrelsection 33 moving upwardly relative to the cutter supporting members 26and allowing the latter to swing inwardly to retract the cutters 29.Thus, the drill string B and the bit assembly may be pulled from thecasing or pile D.

If it is desired to pull the valve sleeve 90 during servicing of the bitat the top of the well, such pulling may be accomplished by the pullingtool P, as previouslyfdescribed and as shown in FIGS. and 6. I

When the newly serviced or a new bit is to be run back into the boreholeto continue the drilling operation, such bit will be connected to thelower end of the drill string with the valve sleeve 9% in the lowerposition shown in FIG. 2, and the bit assembly run into the boreholewith the cutters retracted. The plugging device 125, if not initiallyplaced inits seat 100a, may then be dropped through the drill pipeand-onto the seat 100a of the boss 41 of the lower mandrel section 33.Liquid may then be placed in the drill string to fill the chamber 55with fluid at sufficient pressure to effect relative upward movement ofthe bit body 13 along the mandrel and expansion of the cutters 2?.Thereupon, the tool T will be run into the drill string and-engaged withthe latch means 95, as previously described, to move the valve sleeve 90upwardly, thereby closing off the ports 62 and trapping the liquid inthe chamber 55. Further upward movement of the tool T will effect itsrelease from the latch means and the tool T may be recovered. Thereupon,the plugging device 125 will be recovered, allowing such liquid asremains in the drill string to flow therefrom. Drilling may then beresumed employing suitable drilling fluid, such as air or gas, to removethe cuttings from the borehole. Since the cutters are hydraulicallylocked intheir outward or expanded positions, it is unnecessary that thefluid circulating equipment or compressors be of such output capacity asto create sufflcient differential pressure across the flow restrictor7b, as would otherwise be necessary to effect expansion of the cutters.If the bit is picked up off of the borehole shoulder E, the cutters 29are prevented from retracting, being retained in their maximum outwardlyexpanded condition.

1. in a rotary drill bit connectable to a rotary drill string fordrilling a borehole in the earth: a main body, laterally movable cuttermeans carried by said body, means for expanding said cutter meanslaterally of said body from a retracted position to an expandedposition, and means for releasably retaining said cutter means in saidexpanded position comprising means providing a hydraulic fluid chamberand a passage leading from said chamber, and releasable means forclosing said passage to prevent fluid from entering saidchamber from anysource and to trap hydraulic fluid in saidcharnber to retain said cuttermeans in expanded position, said closing means being movable from itspassage closing position.

2. In a rotary drill bit as defined in claim 1; said expanding meanscomprising a mandrel movable longitudinally within and relative ,'tosaid body, said body and mandrel providing cylinder and piston meansresponsive to fluid under pressure in the borehole for effectingexpansion of said cutter means, said cylinder and piston means togetherwith said body and mandrel providing said hydraulic fluid chamber.

3. In a rotary drill bit as defined in claim 1; said expanding meanscomprising a mandrel movable longitudinally within and relative to saidbody, said body and mandrel providing cylinder and piston meansresponsive to fluid under pressure in the borehole for effectingexpansion of said cutter means.

4. In a rotary drill bit connectable to a rotary drill string fordrilling a borehole in the earth: a body having cutters carried therebyfor expansion from a retracted position laterally outwardly to expandedpositions; means for expanding said cutters, including a tubular membermovable relatively longitudinally in said body; said tubular member'having a fluid passage therethrough communicating with said drillstring for the flow of drilling fluid; said body and said member havingmeans defining a fluid chamber therebetween and having pressureresponsive surfaces for holding said body and said member in relativelongitudinal positions with said cutters expanded, a port communicatingwith said chamber, and means for closing said port to prevent fluid fromentering said chamber from any source and to trap fluid in said chamberwith said cutters expanded.

5. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and

-19., said means for trapping fluid in said chamber including a sleeveshiftable in said passage between a first position at which said port isclosed and a second position at which said port is open.

6. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, and means for releasablyholding said sleeve in said first position.

7. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage 'in said member, said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, means for releasably holdingsaid sleeve in said first position, and means adapted to be disposed insaid passage and engageable with said sleeve to move said sleeve fromsaid first position to said second position.

8. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, said sleeve and said memberhaving cooperative latch means for releasably holding said sleeve insaid first position.

9. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and

said means for trapping fluid in said chamber including asleeveshiftable in said passage between a first position at which said port isclosed and a second position at which said port is open, said sleevehaving a plurality of circumferentially spaced flexible arms projectinglongitudinally in said passage,

1 said member having an internal groove in said passage, and

said arms having external lugs engageable in said groove for holdingsaid sleeve in said first position.

10. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, said sleeve and said memberhaving cooperative latch means for releasably holding said sleeve'insaid first position, and tool means for engaging said sleeve to releasesaid latch means and move said sleeve longitudinally in said passage.

11. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member,

. and said means for trapping fluid in said chamber including a sleeveshiftable in said passage between a first position at which said port isclosed and a second position at which said port is open, said sleeve andsaid member having cooperative latch means for releasably holding saidsleeve in said first position, and tool means for engaging said sleeveto release said latch means and move said sleeve longitudinally in saidpassage to said second position.

12. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, said sleeve and said memberhaving cooperative latch means for releasably holding said sleeve insaid first position, and tool means for engaging said sleeve to releasesaid latch means and move said sleeve longitudinally in said passage forremoval from said passage.

13. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, said sleeve having aplurality of circumferentially spaced flexible arms projectinglongitudinally in said passage, said member having an internal groove insaid passage, and said arms having external lugs engageable in saidgroove for holding said sleeve in said first position, said sleeve alsohaving internal abutment means, and tool means adapted to be disposed insaid sleeve and having means engageable with said internal abutmentmeans to release said external lugs from said groove to move said sleevein said passage.

14. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, said sleeve having aplurality of circumferentially spaced flexible arms projectinglongitudinally in said passage, said member having an internal groove insaid passage, and said arms having external lugs engageable in saidgroove for holding said sleeve in said first position, said sleeve alsohaving abutment means, and tool means adapted to be disposed in saidsleeve and having means engageable with said abutment means to releasesaid external lugs from said groove to move said sleeve in said passageto said second position.

15. In a rotary drill bit as defined in claim 4; said port leadingbetween said chamber and said passage in said member, and said means fortrapping fluid in said chamber including a sleeve shiftable in saidpassage between a first position at which said port is closed and asecond position at which said port is open, said sleeve having aplurality of circumferentially spaced flexible arms projectinglongitudinally in said passage, said member having an internal groove insaid passage, and said arms having external lugs engageable in saidgroove for holding said sleeve in said first position, said sleeve alsohaving internal abutment means, and tool means adapted to be disposed insaid sleeve and having means engageable with said internal abutmentmeans to release said external lugs from said groove to move said sleevein said passage for removal from said passage.

16. In a rotary drill bit connectable to a rotary drill string fordrilling a borehole in the earth: an elongated mandrel having a fluidpassage therethrough, a body reciprocably disposed on said mandrel,expansible cutter means, means for moving said cutter means to expandedpositions when said mandrel and said body are in one relativelongitudinal position and for allowing retraction of said cutter meanswhen said mandrel and said body are in another relative longitudinalposition, and releasable hydraulic locking means for holding saidmandrel and said body in said one relative longitudinal position; saidhydraulic lock means including a cylinder head on said body, said bodyhaving a cylinder extending axially from said head, a piston on saidmandrel reciprocable in said cylinder, port means leading between saidmandrel passage and said cylinder between said cylinder head and saidpiston, said cylinder head and said piston moving one away from theother upon movement of said mandrel and said body to said one relativelongitudinal position, and valve means for selectively closing andopening said port means, said valve means closing said port means toprevent fluid from flowing from said mandrel passage into said cylinderand from said cylinder into said mandrel passage, said valve meanstrapping fluid in said cylinder when said valve means closes said portmeans.

17. In a rotary drill bit as defined in claim 16; said valve meansincluding a valve sleeve shiftable in said mandrel passage between afirst position closing said port means and a second position openingsaid port means.

18. In a rotary drill bit as defined in claim 16; said valve meansincluding a valve sleeve shiftable in said mandrel passage between afirst position closing said port means and a second position openingsaid port means, and cooperable latch means in said mandrel and on saidsleeve for releasably latching said valve sleeve in said first position.

1. In a rotary drill bit connectable to a rotary drill string fordrilling a borehole in the earth: a main body, laterally movable cuttermeans carried by said body, means for expanding said cutter meanslaterally of said body from a retracted position to an expandedposition, and means for releasably retaining said cutter means in saidexpanded position comprising means providing a hydraulic fluid chamberand a passage leading from said chamber, and releasable means forclosing said passage to prevent fluid from entering said chamber fromany source and to trap hydraulic fluid in said chamber to retain saidcutter means in expanded position, said closing means being movable fromits passage closing position.
 2. In a rotary drill bit as defined inclaim 1; said expanding means comprising a mandrel movablelongitudinally within and relative to said body, said body and mandrelproviding cylinder and piston means responsive to fluid under pressurein the borehole for effecting expansion of said cutter means, saidcylinder and piston means together with said body and mandrel providingsaid hydraulic fluid chamber.
 3. In a rotary drill bit as defined inclaim 1; said expanding means comprising a mandrel movablelongitudinally within and relative to said body, said body and mandrelproviding cylinder and piston means responsive to fluid under pressurein the borehole for effecting expansion of said cutter means.
 4. In arotary drill bit connectable to a rotary drill string for drilling aborehole in the earth: a body having cutters carried thereby forexpansion from a retracted position laterally outwardly to expandedpositions; means for expanding said cutters, including a tubular membermovable relatively longitudinally in said body; said tubular memberhaving a fluid passage therethrough communicating with said drill stringfor the flow of drilling fluid; said body and said member having meansdefining a fluid chamber therebetween and having pressure responsivesurfaces for holding said body and said member in relative longitudinalpositions with said cutters expanded, a port communicating with saidchamber, and means for closing said port to prevent fluid from enteringsaid chamber from any source and to trap fluid in said chamber with saidcutters expanded.
 5. In a rotary drill bit as defined in claim 4; saidport leading between said chamber and said passage in said member, andsaid means for trapping fluid in said chamber including a sleeveshiftable in said passage between a first position at which said port isclosed and a second position at which said port is open.
 6. In a rotarydrill bit as defined in claim 4; said port leading between said chamberand said passage in said member, said means for trapping fluid in saidchamber including a sleeve shiftable in said passage between a firstposition at which said port is closed and a second position at whichsaid port is open, and means for releasably holding said sleeve in saidfirst position.
 7. In a rotary drill bit as defined in claim 4; saidport leading between said chamber and said passage in said member, saidmeans for trapping fluid in said chamber including a sleeve shiftable insaid passage between a first position at which said port is closed and asecond position at which said port is open, means for releasably holdingsaid sleeve in said first position, and means adapted to be disposed insaid passage and engageable with said sleeve to move said sleeve fromsaid first position to said second position.
 8. In a rotary drill bit asdefined in claim 4; said port leading between said chamber and saidpassage in said member, and said means for trapping fluid in saidchamber including a sleeve shiftable in said passage between a firstposition at which said port is closed and a second position at whichsaid port is open, said sleeve and said member having cooperative latchmeans for releasably holding said sleeve in said first position.
 9. In arotary drill bit as defined in claim 4; said port leading between saidchamber and said passage in said member, and said means for trappingfluid in said chamber including a sleeve shiftable in said passagebetween a first position at which said port is closed and a secondposition at which said port is open, said sleeve having a plurality ofcircumferentially spaced flexible arms projecting longitudinally in saidpassage, said member having an internal groove in said passage, and saidarms having external lugs engageable in said groove for holding saidsleeve in said first position.
 10. In a rotary drill bit as defined inclaim 4; said port leading between said chamber and said passage in saidmember, and said means for trapping fluid in said chamber including asleeve shiftable in said passage between a first position at which saidport is closed and a second position at which said port is open, saidsleeve and said member having cooperative latch means for releasablyholding said sleeve in said first position, and tool means for engagingsaid sleeve to release said latch means and move said sleevelongitudinally in said passage.
 11. In a rotary drill bit as defined inclaim 4; said port leading between said chamber and said passage in saidmember, and said means for trapping fluid in said chamber including asleeve shiftable in said passage between a first position at which saidport is closed and a second position at which said port is open, saidsleeve and said member having cooperative latch means for releasablyholding said sleeve in said first position, and tool means for engagingsaid sleeve to release said latch means and move said sleevelongitudinally in said passage to said second position.
 12. In a rotarydrill bit as defined in claim 4; said port leading between said chamberand said passage in said member, and said means for trapping fluid insaid chamber including a sleeve shiftable in said passage between afirst position at which said port is closed and a second position atwhich said port is open, said sleeve and said member having cooperativelatch means for releasably holding said sleeve in said first position,and tool means for engaging said sleeve to release said latch means andmove said sleeve longitudinally in said passage for removal from saiDpassage.
 13. In a rotary drill bit as defined in claim 4; said portleading between said chamber and said passage in said member, and saidmeans for trapping fluid in said chamber including a sleeve shiftable insaid passage between a first position at which said port is closed and asecond position at which said port is open, said sleeve having aplurality of circumferentially spaced flexible arms projectinglongitudinally in said passage, said member having an internal groove insaid passage, and said arms having external lugs engageable in saidgroove for holding said sleeve in said first position, said sleeve alsohaving internal abutment means, and tool means adapted to be disposed insaid sleeve and having means engageable with said internal abutmentmeans to release said external lugs from said groove to move said sleevein said passage.
 14. In a rotary drill bit as defined in claim 4; saidport leading between said chamber and said passage in said member, andsaid means for trapping fluid in said chamber including a sleeveshiftable in said passage between a first position at which said port isclosed and a second position at which said port is open, said sleevehaving a plurality of circumferentially spaced flexible arms projectinglongitudinally in said passage, said member having an internal groove insaid passage, and said arms having external lugs engageable in saidgroove for holding said sleeve in said first position, said sleeve alsohaving abutment means, and tool means adapted to be disposed in saidsleeve and having means engageable with said abutment means to releasesaid external lugs from said groove to move said sleeve in said passageto said second position.
 15. In a rotary drill bit as defined in claim4; said port leading between said chamber and said passage in saidmember, and said means for trapping fluid in said chamber including asleeve shiftable in said passage between a first position at which saidport is closed and a second position at which said port is open, saidsleeve having a plurality of circumferentially spaced flexible armsprojecting longitudinally in said passage, said member having aninternal groove in said passage, and said arms having external lugsengageable in said groove for holding said sleeve in said firstposition, said sleeve also having internal abutment means, and toolmeans adapted to be disposed in said sleeve and having means engageablewith said internal abutment means to release said external lugs fromsaid groove to move said sleeve in said passage for removal from saidpassage.
 16. In a rotary drill bit connectable to a rotary drill stringfor drilling a borehole in the earth: an elongated mandrel having afluid passage therethrough, a body reciprocably disposed on saidmandrel, expansible cutter means, means for moving said cutter means toexpanded positions when said mandrel and said body are in one relativelongitudinal position and for allowing retraction of said cutter meanswhen said mandrel and said body are in another relative longitudinalposition, and releasable hydraulic locking means for holding saidmandrel and said body in said one relative longitudinal position; saidhydraulic lock means including a cylinder head on said body, said bodyhaving a cylinder extending axially from said head, a piston on saidmandrel reciprocable in said cylinder, port means leading between saidmandrel passage and said cylinder between said cylinder head and saidpiston, said cylinder head and said piston moving one away from theother upon movement of said mandrel and said body to said one relativelongitudinal position, and valve means for selectively closing andopening said port means, said valve means closing said port means toprevent fluid from flowing from said mandrel passage into said cylinderand from said cylinder into said mandrel passage, said valve meanstrapping fluid in said cylinder when said valve means closes said portmeans.
 17. In a rotary drill bit as defined in claim 16; said valvemeans including a valve sleeve shiftable in said mandrel passage betweena first position closing said port means and a second position openingsaid port means.
 18. In a rotary drill bit as defined in claim 16; saidvalve means including a valve sleeve shiftable in said mandrel passagebetween a first position closing said port means and a second positionopening said port means, and cooperable latch means in said mandrel andon said sleeve for releasably latching said valve sleeve in said firstposition.